1. Field of the Invention
The invention related to methods and apparatus for the collection and separation of the light liquid phase from the heavy, substantially celluar phase of blood.
2. Brief Description of the Prior Art
The U.S. Pat. Nos. 3,852,194; 3,920,549; and 3,997,442 are representative of the prior art. In general, the prior art apparatus comprises a tubular container into which there is inserted a gel-like barrier material having a density intermediate between that found for the light, liquid phase and the heavy, substantially cellular phases of blood. Generally, the gel-like material is disposed at the bottom end of the tube and then the tubular collection container is filled with blood. Upon centrifugation, the blood is gradient separated into its two phases and the gel-like barrier material migrates to the interface between phases. Upon completion of centrifugation, the gel-like barrier material forms a physical and chemical barrier between the separated blood phases.
On occasion, there is difficulty with the prior art methods and apparatus in establishing a complete barrier with the gel-like material between the separated blood phases. This is particularly so when the tube is centrifuged in a fixed angle head centrifuge. In such instances there is a tendency for the gel-like barrier material to migrate to its final position along one portion of the inner wall of the tubular container. When the gel-like material reaches the zone for its density gradient, it may not migrate completely to the opposite wall of the tubular container to affect a complete barrier between the separated blood phases. If the gel-like material does reach the opposing tubular wall, it may not adhere sufficiently so that in subsequent handling it will peel back and off the opposing wall. This of course is undesirable under many circumstances.
By the method of our invention, the above described difficulty of the prior art is obviated. A strong bond is obtained between the gel-like barrier material and the entire surrounding walls of the tubular container. This is particularly advantageous if the collected blood specimen is to be stored for a long period of time, or is likely to be subjected to temperature shocks during storage or shocks due to transportation.